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more engine design options

ryan22re

ryan22re

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the more and more i think and read about it the more and more i want to build a smaller low rpm engine. i keep reading about how manufacturers are increasing the length of the strokes. from what i can understand, this leads to reduced emissions, which means to me a more complete burn and as a by product is more power. sure the stroke gives up some rpm potential, but thats how the little 4cyl hondas are built, and the ecotec, not to mention the 8.1 (496 4.25" bore 4.37" stroke). something to due with longer dwell at tdc and bdc.

heres where i say that due to the recent turn of events and the price of gas...blah blah blah... but im thinking this: a 305 (3.73" bore) or a 307 (3.875" bore) with a 400 crank. the 305 would be about a 334 and the 307 would be right at 350 cid. coupled with a set of vortec heads and a small hyd. roller cam and about 9.5-10:1 compression ratio. not trying to make tons of horsepower, but i think that this combo could make 250-260 hp and around 310-320 ft-lbs. and be as much or better in fuel mileage as my current 350 (old and worn out). has anybody tried this? am headed in the right direction? does anybody care about building 305s and 307s?

ryan
 
from what ive been told your right but i think you might have some clearance problems with that long of a stroke otherwise i'm interestead in how it would turn out
 
thing would not like rpm thats for sure, o yeh a 496 is typically built 4.310 bore, 4.25 stroke. Never seen one at 4.25/4.37...not sure if the math even works. If I get a few spare minutes ill run it through desktop dyno and see what this engine gets.
 
k20 said:
thing would not like rpm thats for sure, o yeh a 496 is typically built 4.310 bore, 4.25 stroke. Never seen one at 4.25/4.37...not sure if the math even works. If I get a few spare minutes ill run it through desktop dyno and see what this engine gets.
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thats what gm lists for the 496(8.10 in the new trucks

ryan
 
Dont know..

A 307 might not accept the stroke of a 400 crank--it might hit the block near the pistons..they were a short stroke hi rev motor..most all chevy small blocks were high rpm short stroke except the 400 small block..the 305 and 350 share the same stroke,only the bore is smaller,and heads are different size valves..better off making a 383 "stroker" out of a 350 if your going to all that trouble..gas mileage is a moot point,all long stroke motors like to drink...

If a long stroke,high low rpm torque motor is what your after,maybe an inline 6 cylinder engine is what your looking for--like the 292 Chevy 6..a 4-1/8 " stroke!..and around 250-300 ft lbs at 1600 rpm stock!...I have had a few very fast rides in a 292 equipped 66 Chevy Nova!..but be aware they are not very good on gas--15 mpg is about the best you can expect from one if you drive it gently--that long stroke== a deeep breath every time the piston goes down,and it can inhale a lot of fuel/air mix!..they can be beefed up with domed pistons and a hi lift low duration cam,and 2 or 4 bbl carbs and intakes--Clifford Research has a lot of "hop up" stuff for inline sixes.. :crazy:

If you want a mildly powerful motor that gets excellent gas milage,a 283 or 307 with low rear end gears will give decent performance and mileage..a 2 bbl 283 put out 195 hp,and about 250-275 ft lbs of torque..a 307 puts out 200 hp and 300 ft lbs..in stock form--they will give 15-20 mpg under ideal conditions..and still have adequate power,if the gearing isn't too high!-(dont put a 2.73 rear end in,like I did in my van--its a DOG!--and gets 13 mpg,no matter what.. :doah: )..
 
diesel4me said:
gas mileage is a moot point,all long stroke motors like to drink...
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not necesarily true, there are too many variables to make a blanket statment like that without more input, nice try though.
 
k20 said:
Ok, all these numbers should be taken with a grain of salt, but just quick throw together of a 305 bore and a 400 stroke, 9:1, vortec heads, headers, and a quick cam grab, it made 403ft/lbs@2000rpm and 262hp@4000rpm and its 328.7ci btw.
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yep, thats what i am after. and i think a 334 is .030 over.

i plan on putting my k5 on a major diet, so it wont be comparing apples to apples, but i think that it is a do-able proposition to have decent power and good fuel economy.

ryan
 
I think taking a cue from the LS series of motors is probably the best approach. Since they've already been built and can be bought, that's probably a good way to go.

Problem with the 305 and 307 is the bore size. Even in that article they mention the valves being shrouded, and that happens in a small bore engine with big valves.

I would ASSuME that the ecotecs and what not are overhead cam engines, some engines using variable valve timing, all using port fuel injection, along with engines based on modern design theory. (stroke, combustion chamber, pistons, etc)

I know nothing about the smaller engine designs for the most part, but smaller displacement equals greater fuel economy. We're talking 35+ MPG out of a 1.3 liter engine (or so) while we are STILL talking about 5+L engines.

Vehicle weight is a huge problem, as is aerodynamics, neither of which will be solved with our trucks.

Worn 305 to worn 350, I netted slightly better economy with the 350. Remains to be seen whether port injection, increased compression, slightly larger bore, and roller internals will make my new 350 more efficient than the previous carbed version. Mine was built with economy in mind, but I'd be astounded anymore if I could get over 20MPG on flat ground at cruise.

What do you get now? 18MPG is do-able with a basic carbed 350.
 
could be..

beater_k20 said:
not necesarily true, there are too many variables to make a blanket statment like that without more input, nice try though.
Click to expand...

Yeah,it might not apply to ALL engines with long strokes,but most--my brothers 42 Studebaker inline 6 has a long stroke(not sure of exact specs,but its long!) and it gets 20+ mpg easily--its only 170 cubes though!..most all early cars with inline engines used long strokes,and had great low rpm torque,even 4 cylinders..

All the long stroke motors I've had like 292's,the 400 small block,and 454's all were not that great on gas--but I WAS suprised when I put the 454 in one truck,and got better mileage than it did with a 350..only because it didn't have to work as hard I suppose..I was dissapointed with th 292's fuel mileage-( but not its torque!)--the 454 almost beat that motor as far as gas mileage too! :crazy:
 
diesel4me said:
All the long stroke motors I've had like 292's,the 400 small block,and 454's all were not that great on gas--but I WAS suprised when I put the 454 in one truck,and got better mileage than it did with a 350..only because it didn't have to work as hard I suppose..I was dissapointed with th 292's fuel mileage-( but not its torque!)--the 454 almost beat that motor as far as gas mileage too! :crazy:
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i'm not saying that a long stroke gets better fuel mileage. im saying that a long stroke coupled with a bore roughly the same size or smaller may get better fuel mileage. im thinking the shrouding of the valves, while it may hurt flow, aids in turbulence and in turn, fuel economy. last time i checked, both the 400 and 454s had bores bigger than the stroke. so why does it matter that they weren't that great on gas?

ryan
 
ryan22re said:
the more and more i think and read about it the more and more i want to build a smaller low rpm engine. i keep reading about how manufacturers are increasing the length of the strokes. from what i can understand, this leads to reduced emissions, which means to me a more complete burn and as a by product is more power. sure the stroke gives up some rpm potential, but thats how the little 4cyl hondas are built, and the ecotec, not to mention the 8.1 (496 4.25" bore 4.37" stroke). something to due with longer dwell at tdc and bdc.

ryan
Click to expand...

Well first of all.

As a former honda guy :doah: (I know, I know) The major lacking of most of the honda motors is stroke. Everyone hates them cause of no torque.

BTW There is so many ways to make good power from a bolt-on 350. Why would you want a science project under your hood?

K.I.S.S. You'll thank yourself for it

Edit: Come to think of it. My first car ('77 T/a) I had swapped out the 400 for a pontiac 455. Now it had a 2.41 gear in the back but with just a th350 it would get round 18mpg on the highway. Just some insight I guess..
 
Modern designs of cylinder heads (fastburn) take care of the problem of mix without the downsides of shrouding the valves. GM tried to do the same thing with the TBI heads without messing with the chamber, we know how bad they suck.
 
Big89Burban said:
Edit: Come to think of it. My first car ('77 T/a) I had swapped out the 400 for a pontiac 455. Now it had a 2.41 gear in the back but with just a th350 it would get round 18mpg on the highway. Just some insight I guess..
Click to expand...

yep and the pontiac 455's had a 4.15 inch bore and a 4.21 inch stroke (dont quote me on that one though but i think thats what it was). take an engine with alot of torque and gear it accordingly.

ryan
 
I think it is an interesting Idea at least to stroke a smaller cube sb. Keep in mind this is nothing new, rodders in the early 60's were stuffing 327 cranks in 283's. Hmm, come to think of it the 302 came about in that kind of fashion...

I had a 307 in my 69 Nova and with nothing more than a cast iron 4bbl intake and a q-jet it would knock down 20 mpg on the highway at 80mph. Of course 2.73 gears helped, but it also made it an absolute DOG out of the hole. Throwing a 400 crank wouldn't be any more difficult than on a 350 as you end up clearancing everything on the block anyway. Use the vortec heads off of a 305 vortec (that is if they had smaller valves than the 350 version, for less shrouding in the small bore) and you could have one little torque monster.

Keep this in mind on the 307's though. It's commonly known that the 307 blocks were cast with lower nickel content than the 327/350's of the same era. This made the 307's less durable than the others. Now my 307 (still sitting on a stand in my dad's garage) was punished by me as a teenager. From revving the snot out of it in low trying to race to running it low on oil (burned it like crazy) for miles with the oil light on trying to kill it, it would not die. Yes it leaked oil from every seal, burn what was left by the rings and had dribbles of antifreeze from each freezeplug but it still ran like a timex. How, I won't know. But I bet it would fire up today with a fresh change of plugs, oil and a carb. I'm sure the oil burning was due to poor ring seal on cylinders that are less than round due to the 307 block.

I'd go with a 305 as a base as they are more plentiful, plus if you go for a later version, you can get the added benifits of the roller cam too.
 
Big89Burban said:
Well first of all.

As a former honda guy :doah: (I know, I know) The major lacking of most of the honda motors is stroke. Everyone hates them cause of no torque.

BTW There is so many ways to make good power from a bolt-on 350. Why would you want a science project under your hood?

K.I.S.S. You'll thank yourself for it
Click to expand...

actually those 1.8's that those honda guys swap all the time have a 3.189 inch bore and a 3.433 inch stroke. which would make them undersquare. the 1.6s are almost square.

i dont really want a science project. i want a torquey fuel efficent v8. dont really care how i get there. but i think that the engine i propose to build will make more torque at a lower rpm than a 350 would. and perhaps get better fuel mileage. and the only real extra cost to build the motor would be the crank.

ryan
 
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